It seems that this was a bug even in the python interface. So this simplification should be effective. And also, I do not think that this will create problems in speed. 
I'm not that familiar with this part of blender, but poking around at the buttons just seems like a misunderstanding.
Yep, indeed after testing in fixed build it really look like duplicate of blender/blender#106982 and that fixed in today 3.6 build, and will be pushed in 3.5.
Funny bug, thanks for the report, I'll check later. But this is very close to the truth.
This is not very practical, because in fact, it cannot be applied to the properties of an object, for example? Is it possible to make property references without statically specifying the structure type? It seems one of the node_layout arguments might be useful. That is, it seems that the update function should do this itself and pass in RNA_property_subtype_set prop as argument?
Hello, thanks for report but that is not a bug. Internally this any angle-base value is radians. But you can choose way to show this in interface in scene popertyes: 
This seems to have been fixed, can you test it in today's 3.6 build?